Immunizations or vaccinations if needed should be taken least 6 weeks before you leave. Some vaccines need about 6 weeks after you get the shots to reach to the highest protection level.
Medical and dental check-ups are important before your trip, to be aware of problems if any. Then accordingly you can find out about medicines you might need to take along.
Enquire fully about your health insurance, in case you might see a doctor while you’re in another country. Carry enough of your regular medicines in their original containers, along with extra prescriptions for them. Also bring your eyewear prescriptions. Do bring a first-aid kit along.